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Photodynamic therapy (PDT) is an effective treatment method for various
types of invasive tumors. The efficiency of PDT treatment depends, to a
great extent, on optimal dosimetry of light, the photosensitizer used, and
on tissue oxygenation. Fluorescence spectroscopy can be employed for
measurement of drug concentration in target tissue and can provide a
basis for in vivo evaluation of treatment efficiency. We have developed an
integrated system that can be used to determine photosensitizer
concentration in vivo based on fluorescence measurements. In our study,
we performed fluorescence measurements on colon tumors of Balb/c mice
in which CT26 cells were injected subcutaneously in the right flank. 5-
Aminolevulinic acid (ALA)-induced protoporphyrin IX (PpIX) was used
as the photosensitizer. ALA was administered intraperitoneally at a dose
of 200 mg/kg and PpIX fluorescence profiles were followed up to 34 h after
ALA administration. Maximum fluorescence intensity was found 8 h after
ALA administration. Also, we determined the relationship between PpIX
concentration in colon tumor tissue of Balb/c mice and its fluorescence
intensity at the peak of the spectrum (635 nm). This was used to determine
the PpIX content in the target tissue as a function of time after ALA
administration.